Going to be getting a new processor and mobo soon.
Also should I buy it from Amazon or Newegg ?
You don't say what you are going to be doing with it which makes a recommendation between AMD and Intel difficult. Personally, I don't give a crap about games but if you do that may change the answer. My old CPU was an I7-2600K which I chose over an i5 (in 2011) do to the i7 having more threads. So recently when I started looking to upgrade, I naturally gravitated to the 7700K. But then the Ryzen 7's came out with 2x the cores and 2x the threads (remembering that thats what counts for me). My local Microcenter has the 7700K for $299 and the R7 1700 for $329. So the R7 1700 was starting to look pretty good. But then the R5's came out and I ended up with an R5 1600. 6C12T for only $219. So for my purposes that was a way better deal than the 7700K. Then throw in that I got a decent AM4 motherboard for $39 as part of a bundle with the CPU and its hard to beat on price/performance ratio.
Wait? Not me. I usually decide based on what I can buy today. I guess if I really wanted Intel and the new 6C12T Intel CPU's were coming out in a month or less then a month I might consider it. But I wouldn't wait long. The other thing is that the new Intel generation is vapor right now. I also don't buy until at least the major review sites have bench marked a real world sample - which they did right before I bought the R5. But its up to you.
Where to buy.
1. Microcenter if you live near one. They always have great MB/CPU bundles on both Intel and AMD CPU's. I say if you live near one because their best deals are in store only.
2. Amazon. Others have talked about the tax issue. I can't help you with that because I don't live where you do. But I like both Amazon and Newegg. Newegg used to be my go to online place but nowadays Amazon is usually cheaper.
3. Newegg. I find it easier to shop on newegg. Its easier to find just want I want and to compare products on their site. I usually start there researching prices, user reviews etc but once I've selected a product I go check the price on Amazon and lowest price wins.
Note: When I say lowest price I mean lowest price delivered to my door. I always include sales tax (if any) along with shipping charges and base the real price on the total amount I'm going to pay.
4. Others. I probably wouldnt buy a CPU other than 1, 2, and 3 above. If I'm going to try out a new vendor I usually give them a smaller order or two to see how it goes before I buy anything big from them. But its been a long time since I've bought from anyone but 1, 2, and 3 and all my CPU's and motherboards have come from Microcenter. Looking at total price, even though they will charge me sales tax, they have always still come out the lowest price for bundles.